Sponges reproduce asexually by a mode of budding and growth similar to that just de scribed or, as especially exemplified in the fresh water sponges, by the formation of gemmules which are complexly formed buds protected by a spicule-sheath and capable of developing into a complete sponge colony. They also reproduce sexually by the union of ovum and sperma tozoon which develops into a free-swimming ciliated larva (planula), serving not only to reproduce the species but through its activity to distribute these fixed and stationary animals. Except a few small fresh-water species all of the sponges are marine, and occupy all seas from the shores to great depths. It is in tropical and subtropical regions, however, that they are es pecially prominent. Remains of fossil sponges in great number and variety, some of them rep resenting extinct types, occur in all geological formations from the Cambrian upward.
The phylum Porifera has been classified as follows: Class I. Calcarea, including sponges with calcareous spicules, such as the little Grantia ciliata, so common on the New England coast.
Class II. Hexactinellida, including sponges with silicious usually six-rayed spicules, such as glass sponges and the beautiful Venus' flower basket (Euplectella) of the Japanese and Philippine seas.
Class III. Desmospongice, including all other sponges with horny or silicious skeletons, and divided into the following three grades: (1) Tetraxonida, with tetraxial silicious spicules; (2) Monaxonida, with uniaxial spic ules, including the fresh-water sponges. (3) Keratosa, with a skeleton of spongin fibres, in cluding all of the commercial and related sponges.
The sponges of commerce come from the eastern Mediterranean the West Indies, and the coasts of Florida and Central America. In the Grecian Archipelago, Crete, Cyprus, on the coasts of Asia Minor, Syria, Barbary and the Bahama Islands, sponge fisheries constitute a very important industry. The finest sponges are obtained in Turkish waters. The fishing season commences in May and closes in Sep tember or October. Diving is practised and is carried on in a rude, primitive manner. The diver, who has no dress, seizes hold of a large stone, to which a line is attached, and sinks by means of it to a depth varying from 30 to 180 feet. Keeping hold of the rope, he tears the sponges off the rocks within his reach and places them in a net; when he has secured a netful he signals by means of the rope to be drawn up.
Modern diving dresses have been introduced successfully in some places. The West Indian trade is annually increasing and the fishing in dustry gives employment to 500 boats and over 2,000 persons. The Bahamas and the coast of
Florida are the best fishing grounds.
Florida is the only State in the Union which has a sponge-fishery, and there it is confined to the southwestern part of the coast, along the reefs and to the extensive rocky shoals that lie between Saint Mark's and Anclote Keys. The former is known as the Key ground, with its centre at Key West, the latter as the bay ground with its centre at Tampa Bay.
Nearly all of the sponges used in the United States were brought from the Mediterranean till 1852, when attention was called to the im mense numbers that were growing in Florida waters. As soon as it was found that the qual ity of these compared favorably with those of Europe the merchants and fitters-out of vessels of Key West engaged very actively in the busi ness of placing them on the market. At first the best qualities were bought from the fisher men at the rate of 10 cents per pound. As Mediterranean sponges became scarce and costly the Florida sponges came into more and more demand and their value increased proportion ately. After about 18 years' fishing on the known ground the supply began to fail. Then, in 1870, a new area of ground, larger than the old one, was discovered, and this gave a new impetus to the trade. In that year Appalachi cola sent out a small fleet of sponge vessels which has since been largely increased and the industry has been energetically pursued with good results.
The methods employed in the fishery differ greatly from those employed in the Mediter ranean. Small vessels, carrying crews of from 5 to 15 men, are fitted out for trips of from four to eight weeks on the sponge grounds. The crews are paired off into small rowboats, or ‘'dingies,” to catch the sponges. One man stands in the stern, sculling the boat, while the other kneels in the bottom amidship, leaning over the side and scans the bottom of the sea by the aid of a water-glass. When a sponge is sighted the boat is stopped and the kneeling man uses a three-pronged hook, attached to a slender Dole 30 to 50 feet in length, to secure it. Consider able dexterity is required of both men. To cure the sponges they are first spread about the vessel's deck in their natural upright position, so that they will die, and while decomposing allow the softened animal matter to run off freely. When they have been several days in this position they are taken to the shore and thrown into the water in little pens called (corrals) where the remaining sub stance is soaked and squeezed out, after which the sponges are removed at intervals and beaten with a stick to facilitate the process.